Gate valves are used in the oil and gas industry. In some situations they can be used in conditions where the fluid may contain particles. A fluid with particles can cause erosion of the gate and seats of the valves during operation and cause damage to and failure of the valve. For prevention of sticking and galling in said gate valves, a coating of tungsten carbide or a hard-facing is typically applied on surfaces subject to sliding in operation.
A prejudice exist against coating further surfaces in a gate valve because further coating is considered to be superfluous since it is not assumed to have any effect. More specifically, other parts of the valve are assumed to have no benefit of coating and are assumed to have a service life as long as the rest of the components or elements of a subsea production system. Or in other words; only surfaces subject to sliding action during operation are considered to have a requirement for coating or hard-facing, not non-sliding surfaces like the internal flow bore of a gate valve.
However, testing has revealed that gate valves can fail far earlier than expected.
The objective of the invention is to provide a gate valve having improved service life and operational characteristics over prior art gate valves.